Pulp molding die



June 10, 1952 PULP MOLDING DIE Filed March 27. 1947 Egi i; 17 wi l /10 ?e 4 30 /14 'I L:

14 16 7 j %WM/m mu-5)? /PANDALL Patented June 10, 1952 PULP MOLDING DIE Walter H. Randall, Waterville,

Maine, asslgnor,

by mesne assignments, to The Canal National Bank of Portland, a national banking association, and William B. Nulty,

trustees Portland, Maine, as

Application March 27, 1947, Serial Ne. 737508 1 Claim.

This invention relates to pulp molding dies and is a continuation-in-part of my prior application S. N. 465210, filed November 11, 1942, now Patent No. 2,424,189, dated July 15, 1947, to which reference is made for a general discussion of the problems in the art when using an open-face, split, forming die which has its molding surface subdivided into sections, each covered by a conforming fine wire mesh drainage screen individual thereto.

As in my aforesaid application, the die of my present invention is designed primarily for the rapid and economical production of relatively deep articles having steep side wall angles, of which the familiar drinking cup may be taken as an example. However, my die is not limited to the production of drinking cups but may be used for producing many other molded pulp articles such as bowls, containers and like articles of generally steep side wall, deep cavity, formation.

The general object of my present invention is to provide an open-face, sectional, wire-covered pulp molding die in which the individual wire mesh screen coverings for the die sections may be readily conformed, without substantial distortion, to the sectional molding surface of the die; to provide a die in which the die sections and their wire mesh coverings will be positively retained in place during the operation of the die With the minimum amount of flexing and consequent distortion of the wire mesh coverings relative to the molding surface of the die; and to provide a die which may be readily assembled and disassembled with the minimum of time and effort when changing dies on the pulp molding machine or when replacing screen coverings which have become worn in service.

Other objects and advantages oi my present die will appear as this description proceeds.

In the accompanying drawing wherein I have illustrated a preferred embodiment of my invention- Fig. 1 is a vertical section through an open-face pulp molding forming die and associated parts in accordance with my present invention.

Fig. 2 is a perspective view of the individual wire mesh covering for the side wall of my die, as shaped for application thereto, and

Fig. 3 is a transverse section on the line 3-3 of Fig. 1 looking in the direction of the arrOWs.

In attaining my objects I construct the molding surface of my die in two sections viz. a wall section and a bottom section, with individual wire mesh coverings for each section, and detachably clamp the two sections and their wire mesh coverings to each other so that the die may be conveniently inserted into and withdrawn from the die body as a, unit and so that the parts of the die may be quickly and easily assembled and disassembled when removed from the machine for the purpose of changing wires.

The wall section of my die is constructed as a single piece and is shown as provided at it-s upper and lower ends with horizontally extending 'peripheral portions which are intersected by a single lengthwise extending slot or groove. Preferably, the conforming wire mesh covering for this side wall section is also constructed as a single piece of wire mesh screen, the longitudinal edges of which are bent to provide abutting lengthwise extending fianges to be inserted and anchored within said longitudinal slot or groove of the side wall section, and the top and bottom edges of which are bent to provide horizontally extending flanges which overlie the corresponding peripheral portions of the side wall section when the wire mesh covering is applied to the side wall section.

For removably holding the wire mesh covering assembled to the wall section before said section is assembled with the bottom section and its individual wire mesh covering and before the die unit is inserted within the die body, I prefer to provide the wall section, adjacent to its lengthwise extending slot or groove, with removable screws or equivalent fastenings, for closing said slot or groove upon the inserted lengthwlse extending flanges of the wire mesh covering.

For removably holding the wall section and its individual wire mesh covering assembled to the bottom section and its individual wire mesh covering before the die unit is inserted within the die body, I fasten the wall and bottom sections together by screws or equivalent fastenings, preferably extending through the peripheral portion, at the lower or inner end of the side wall section and the adjacent marginal portion of the bottom section.

For insuring that the assembled die unit will be positively retained within the die body, I prefer to machine the external faces of the peripheral portions oi the side wall section and the external face of the bottom section to a close fit With corresponding internal hearing surfaces of the die body so that when the die unit is inserted axiaily into the die body through the upper open end thereof, the engagement of these cooperating hearing surfaces with each other will assist in maintaining the several parts of the die unitjin &been inserted thereintc and is fully seated therein. one pronounced advantage construction is that spare dies, in which the mesh screen coverngs have of the afore'said been already made up andfitted to their respective die sections 'and the dies assembled as units, may be carried in stock so that when die repl'acements on the pulp molding machine are necessary the replacement die may be quickly inserted into the 'die block of the machine by merely removing the conventional forming die ring which clamps the die within the die body, withdrawing the used die from the die block, inserting the replacement die, and replacing the ring.

In this connection, it will be understood that with a die of the sectional wire-coverecl type, practical-ly the only Operating maintenance is the necessity of changing worn or damaged'wires. Heretofore when this necessity arose, the machine not only had to be stopped until the die containing the worn wire was withdrawn from the die block but had to stay out of production until such 'die could be disassembled, the worn wire renewed and the die replaced in the machine.

My ccnstructio'n of the die, with preassemble'd spare die units all ready `for insertion in the'che block of the 'machine when needed, reduces to the minimum the time that the machine has to be o'ut'oi production when changing 'wires of dies of thisgene'ral type as well as enabling the wi're change to be leisurely and carefully made at some 'convenient time and place.

In the illustrated embodimlent of my invention I have 'indicated generally at ili the 'die body of my die. Die body o is open at its upper end to permit the die proper, indicated generally at H, to be inserted axially into and withdrawn from the die body for purposes of replacement or repair. such open end 'also permits pulp to 'be deposite'd on the molding surface of the die when the die unit is immersed in the pulp bath and the formed article tobe removed from the -die when the die is withdrawn from the bath.

Die body :a establishes a chamb'er 12 surrounding-the die proper, within whichsub atmospheric and super-atmospheric 'pressures maybe alternately created, as through conduit t, for -the suction formationof an'- article 'on the perforated, wire-covered molding sur-face of the -die and 'for the subsequent -removal of the formed article therefrom. i

The bottom of die body lil may 'be provided with a plurality of spaced upwardly extending lugs M and with a central upstanding lug !5.

The die proper consists of a bottom section IE and a one-'piece wall section l'l. Sections v I@ and '11 "are perforated 'for drainage and are detachably fastene'd together in 'any suitable mann'er 'as by means of the screws !8 or equivalent fastenings.

'Bottom `section IE 'is supported at spacedintervals *about 'its perimeter 'on the lugs s 'or "die body ll) 'and has a central depending stud !9 Iorsupport on lug !5.

Side wall section l'l has a longitudina'l slot or groove 20 therein'extending 'from top to bottom thereof, and is 'alsoprovided at its top and bottom ends with horizontally'extending annular peripheralportions or 'fianges z "and 22 respectively. 'The outer faces "of "these "peripheral p portions and the outer face oi the bottom section !6 are all machined to a close fit with corresponding bearing surfaces IO' and 14' on the die body lil and lugs !4 respectively. If desired, side wall section ll may be provided with longitudinally spaced circumferential stiffening ribs 23, and circumferentially spaced, longitudinnal stifi'ening ribs 23c.

Each die section l' and H is covered by an individual conforming wire mesh screen 24 and 25. Screen covering 24 for the bottom section is preferably a one-piece member and has a marginal portion26 which extends beneath the adjacent peripheral portion 22 of the side wall section ll.

Screen covering for the side wall section l'l is likewise preferably a one-piece member which when shaped to t inside of the side Wall section l'I (see Fig. 2) has its longitudinal edges bent to form a pair of lengthwise extending abutting fianges 21 and 28 and its top and bottom 'edges bent to form a pair of `horizontally extending top and bottom fianges 29 and 30, respectively. Screen '25 is applied to side wall section H by inserting it axially into said section through the upper open end thereof with its lengthwise extending flanges 21 and 28 lodged within the slot or groove '20 of said section (see Fig. 3'). This brings its top fiange 29 against the top face of the peripheral portion or flange 2l of said section H, after which fiange 30 is bent as shown in Fig. 2 so as to abut the under face of peripheral portion 22 of section ll.

For holding cover-ing 25 within the 'side wall section ll', I preferably employ astenings, such as the screws 31 or their equivalent. These extend transversely through oppositely disposed pairs of lugs 32 formed externallyof the side wall section H adjacent the slot or groove 20 at longitudinally spaced intervals. By tightening these screws the slot or groove 29 Will be closed upon the longitudinally extending fianges 27 and 28 oi? said covering 'to thereby clamp the covering securely within said side wall section.

Side wall section !T and its covering 25 may now be fastened to bottom section 16 'and its covering *24 by meanso the screws le. In this position of the parts, the bottom flange 39 `of covering 22:35 overlies 'the marginal portion 25 of'coverin I have indicated at 33 'a conventional die ring for 'ciening the 'edge of the nolded article. Ring 33 is adapted to be removably fastened to the upper open end of the die body 'by meansof threade'd studs 3401' the like.

In assembling my die unit, the wire meshscreen 25 is first assembledto the side wall section H, as described. The wire mesh screen 24 -for the bottom section GG -is then 'applied to the bottom section, and said secticn e and -its screen '24 are then assembled to the side wall section'and its screen by means of the screws !3.

The assembled die unit is now ready to beinserted into'the die body through the upper open end thereof. In this action, theexternalbearing surfaces of the perpheral portions 2! andgz'of the side wall section l'l and 'the external surface of bottom section 16 -engage the corresponding internal hearing surfa'ces 'l 9' and M' 'respectively, on the die body and 'hold the 'die sections and their coverin'gs against `lateral movement within the die body. When the die -ring 33 is fastened in place'this ring clamps the topfiange zof covering-z againstthe adjacent 'face of-thetop'pe rphera'l portion 2l-ofside wall *section ll, and

holds the die assembly tightly within the die body.

As a result of this Construction, it is possible to fit and assemble a number of spare die units, consisting of the side wall and bottom sections and their individual coverings, and have them in stock ready for quick replacement on the molding machine when needed. In making such a change, the forming die ring is removed, the used die unit withdrawn from the die body, the replacement die inserted, and the die ring replaced. Thereafter at any convenient time and place, new Wire may be applied to the used die unit and the recovered die placed in stock for re-use. When needed.

Although screws 3l are provided for holding covering to the side wall section [1 and screws !8 are provided for holding the side wall section to the bottom section !6 while the die unit is operatively positioned within the die body, it will be obvious that once the die unit has been inserted into the die body, the engagement of the complemental hearing surfaces of the die unit and the die body, plus the clamping effect exerted by the die ring, will hold the die unit rigidly assembled within the die body.

The use of these screws however is advantageous for eificiently clamping the die sections and their coverings together as an assembled unit which may be quickly and easily inserted into and withdrawn from the die body in the minimum time and with the minimum loss of machine production as well as for enabling spare die units to be kept in stock for use when needed.

While I have described and illustrated the side Wall and bottom sections as of one-piece construction, it will be obvious to those skilled in the art that these parts, and their coverings, may be of multi-piece Construction, if desired.

Likewise while I have shown my die as designed for the production of cylindrical or tapered articles, it will be understood that the die may be shaped to form articles of other configuration, such as square articles.

The interior molding surface of the wall section l' as shown may be regarded as frusto-conical in shape. As indicated, the cross section of the molding area may be circular, square or otherwise. The term cone" therefore is used in its broad sense as referring to a solid bounded by a circular or other closed plane base and the surface formed by line segments joining every point of the border of the base to a common point called the vertex.

Various other modifications in Construction and design may be made within the scope of my invention as defined by the appended claim.

What I claim is:

In apparatus for molcling brous pulp cupshaped articles, an open face die unit arranged while in assembled condition to be associated with or disassociated from a die body, said die unit comprising. in combination, a unitary, hollow and perforated wall section having an interior molding surface substantially frusto-conical in shape. said wall section having a single longitudinally extending slit throughout its extent to form a slot from the top of the wall section to the bottom thereof, a unitary screen shaped to conform to the inner surface of said wall section and having two longitudinal edges arranged to extend into said longitudinal slot and being further shaped to provide a top flange to overlie the top of the wall section and a bottom fiange to underlie the bottom of the wall section, clamping elements on the Wall section on both sides of the slot for compressing said longitudinal edges of the screen in said longitudinal slot of the wall section, a perforated bottom section shaped to cooperate with said wall section and to form a bottom for the mold cavity, a screen overlying said bottom section the marginal portion of which is arranged to underlie the bottom flange of the wall section screen, and fastening elements secured to said wall section and to said bottom section holding said sections together as a die unit independently of the condition of association or disassociation of said die unit With a die body.

WALTER H. RANDALL.

REFEREN CE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 14,262 Rivers Feb. 20, 1917 '711,165 Howard Oct. 14, 1902 2,192,937 Shepard Mar. 12, 1940 2,320,789 Montague et al. June 1, 1943 42,326,758 Chaplin et al Aug. 17, 1943 2,359,201 Chaplin et al Sept. 26, 1944 2,424,189 Randall July 15, 1947 

